Nov 3, 2026, 9:00 AM
Fall Soil Sampling
Soil sampling can be a low-cost investment with huge returns! Fall is a great time to pull soil samples after harvest. Soil testing is one of the best ways to know what nutrients you have available in your fields to feed your crops. Over the past couple of years, we've been seeing some impressive yields. What are you doing to replenish your soil's nutrient bank?
Before heading out to collect samples, there are a few things to think about.
What Are You Testing For?
Normally, you're testing the levels of nutrients that are less mobile in the soil. These include phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and other micronutrients. It's also important to test your soil's pH and cation exchange capacity (CEC) levels.
When testing phosphorus (P) levels, I would recommend working with your soil testing lab to determine which test is best for your soil. Bray-1, Olsen, and Mehlich-3 are common testing methods, depending on your soil conditions.
How Are You Going to Sample Your Fields?
Now that we have a game plan for what we're sampling and testing for, let's get it done!
The next question is how you're going to sample your fields. There are three common methods to get your results:
- Composite/Field Sampling: This involves collecting one uniform sample to represent the entire field. It gives you a basic overview of your field's nutrient levels.
- Grid Sampling: This breaks your field into smaller, equally sized grids and samples each of those areas. GPS locations are used for this method, allowing you to apply fertilizer where it's needed most.
- Zone Sampling: This method looks at the topography, soil types, and productivity of your field and samples accordingly. It allows you to manage different zones in your field based on their specific needs.
Collecting Your Samples
Now it's time to get out and collect those samples!
Each sample you test should consist of approximately 10–15 soil cores collected throughout the sampling area. This will help give you an accurate result for that area.
When testing in the fall or spring for less-mobile nutrients, you would typically collect a 6-inch soil core. Deeper cores are used when testing for more mobile nutrients, such as nitrate nitrogen.
It's also important to be consistent with your sampling depth and timing each year so you can accurately compare your results.
Summary
Knowing what nutrients you have available in your soil is very important! If your crops are being starved of nutrients, you're going to see it in your yields.
Don't forget about your micronutrients. They may be needed in small amounts, but they're essential to your crop's potential.
Soil testing is an inexpensive investment for the amount of information you receive. Knowing what's going on in your soil will help you make better fertility decisions and give your crops the best opportunity for success.
With the yields we've been pulling, it's important to have a plan to put those nutrients back into the soil for next year's crop!
Sources
